1. Field of the Invention
This invention relates to a fluorescent lamp device, more particularly to a fluorescent lamp device which provides a stronger light output per unit area.
2. Description of the Related Art
Referring to FIG. 1, a conventional fluorescent lamp device is shown to comprise a transparent sealed glass tube 11. The glass tube 11 has an inner peripheral surface coated with a layer of fluorescent material 12, such as a fluorescent metal salt or a phosphorescent metal salt, and is filled with a low pressure working gas 13 that contains mercury vapor. A pair of electrodes 14, 15 are installed respectively at two opposed ends of the glass tube 11 and are connected to a ballast 16 which provides a starting voltage and which limits current flow and to a starter 17 which is used to heat the electrodes 14, 15.
When the lamp device is energized, a low-current glow discharge forms in the starter 17. The heat from this glow is sufficient to form a short circuit through the starter 17. The full output voltage of the ballast 16 then causes current to flow through the electrodes 14, 15, thereby heating and causing the electrodes 14, 15 to emit electrons. At this time, the starter 17 is open circuit and cools. The electrons interact with the mercury atoms of the working gas 13 so as to generate short-wave ultraviolet energy. The fluorescent material 12 on the inner peripheral surface of the glass tube 11 converts the short-wave ultraviolet energy into visible light. However, the intensity of the visible light emitted out of the glass tube 11 is reduced due to the shielding effect of the fluorescent material 12 on the glass tube 11. To increase the intensity of the visible light, the length of the glass tube 11 must be increased so as to increase the amount of the fluorescent material 12. However, increasing the length of the glass tube 11 results in occupying space and in inconvenience of assembly. In addition, it is noted that a conventional fluorescent lamp .device is usually provided on a ceiling such that the upwardly projecting visible light is useless. Although the provision of a reflector on the conventional fluorescent lamp device for reflecting the upwardly projecting visible light has been proposed, the reflector is distant from the glass tube so that the efficiency of the reflector is reduced.